1. Field of the Disclosure
The present invention relates to liquid crystal display devices, and more particularly to a liquid crystal display device associated with a touch panel, in which driving electrodes are formed on an outer surface of a color filter substrate of a liquid crystal panel by patterning for cutting off noise from the liquid crystal panel and fabricating slimmer and more integrated device.
2. Discussion of the Related Art
Currently, as the time turns into a full scale information oriented time, a display field in which an electric information signal is expressed in a visual sensation has been developed rapidly, and, meeting to this development, various kinds of flat display devices have been developed, which have excellent features of slimmer, lighter, and lower power consumption, to replace present cathode ray tube CRT, rapidly.
As specific examples of the flat display devices, there are the liquid crystal display device LCD, a plasma display panel device PDP, a field emission display device FED, and an electro luminescence display device ELD, each of which essentially has a flat display panel in common for producing a picture. The flat display panel is provided with one pair of transparent insulating substrates bonded opposite to each other with a unique light emitting or polarizing material layer disposed therebetween.
Of the flat display devices, the liquid crystal display device displays a picture by controlling light transmissivity of liquid crystals by using an electric field. To do this, the liquid crystal display device is provided with a display panel having liquid crystal cells, a backlight unit for directing the light to the display panel, and a driving circuit for driving the liquid crystal cells.
The display panel is formed to define a plurality of pixel regions as a plurality of gate lines and a plurality of data lines are crossed each other. In this instance, each of the pixel regions has a thin film transistor array substrate and a color filter array substrate opposite to each other, spacers positioned for maintaining a fixed cell gap between the two substrates, and liquid crystals filled in the cell gap.
The thin film transistor substrate is provided with gate lines and data lines, a thin film transistor formed at every crossed portion of the gate lines and the data lines as a switching device, a pixel electrode formed for each liquid crystal cell connected to the thin film transistor, and an alignment film coated on above elements. The gate lines and the data lines have signals supplied thereto from the driving circuit through respective pads.
The thin film transistor supplies a pixel voltage signal supplied to the data line to the pixel electrode in response to a scan signal supplied to the gate line.
The color filter array substrate is provided with a color filter formed for each of the liquid crystal cells, a black matrix for defining the color filters and reflection of an external light, a common electrode for supplying a reference voltage to the liquid crystal cells in common, and an alignment film coated thereon.
By aligning and bonding the thin film transistor substrate and the color filter array substrate fabricated thus individually opposite to each other, injecting the liquid crystals between the two substrates, and sealing the two substrates, the liquid crystal panel is completed.
Recently, requirements for addition of a touch panel to the liquid crystal display device are increasing for perception of a portion of the touch panel touched with a hand or additional input means and transmission of additional information matched to the touch.
Depending on touch sensing types, in the touch panels, there are a resistance type, a capacitive type, and an infrared ray sensing type, and, recently, the capacitive type is paid attention in small sized models, taking convenience of fabrication, sensing capability, and so on into account.
A related art liquid crystal display device will be described with reference to the attached drawings.
FIG. 1 illustrates a section of a related art liquid crystal display device having a touch panel attached thereto.
Referring to FIG. 1, the related art liquid crystal display device is provided with a liquid crystal panel 10 having first and second substrates 1 and 2 opposite to each other, a liquid crystal layer 3 filled therebetween, and first and second polarizing plates 4a and 4b attached to back sides of the first and second substrates 1 and 2 respectively, a touch panel 20 placed on the liquid crystal panel for operating in a capacitive type, and a cover glass 30 on the touch panel for protecting the touch panel 20.
Formed on the first substrate 1 of the liquid crystal panel 10, there are gate lines and data lines perpendicular to each other to define pixel regions, a thin film transistor TFT formed at every crossed portion of the gate lines and the data lines, and a thin film transistor array formed on the pixel region to have pixel electrodes (not shown).
And, formed on the second substrate 2, there are a black matrix layer, color filter layer, and a common electrode (not shown, Vcom (applied voltage)).
The touch panel 20 has an inside structure which is different with types of the touch panel 20. For an example, a capacitive type senses a touch by detecting a capacitance change at a touch point, and has first and second electrodes formed to cross each other and an insulating film formed between the first and second electrodes for sensing the touch by detecting the change of capacitance induced between the electrodes at the time of the touch.
And, in order to protect the touch panel 20, the cover glass 30 is formed on the touch panel 20, additionally.
Formed between the liquid crystal panel 10 and the touch panel 20, there is a shielding layer (not shown) for preventing driving of the liquid crystal panel 10 from giving influence to the touch panel 20. The shielding layer is formed of a transparent electrode to have an adequate thickness for enabling transmission of a picture from the liquid crystal panel 10 therethrough, and preventing driving noise of the liquid crystal panel 10 from entering into the touch panel 20.
In the meantime, the related art touch panel attached type liquid crystal display device requires an adhesive layer between the liquid crystal panel 10 and the touch panel 20. In this case, a step for forming the touch panel 20 is required in addition to the steps for fabricating the liquid crystal panel 10, and a step for attaching the touch panel 20 to the liquid crystal panel 10 is also required.
However, the related art touch panel attached type liquid crystal display device has the following problems.
In the related art touch panel attached type liquid crystal display device, in order to prevent the driving noise of the liquid crystal display device from giving influence to the touch panel, the shielding transparent electrode of an adequate thickness and small resistance is required. However, this case requires not only an additional shielding transparent electrode, but also an additional step for forming the same.
Along with this, the disposition of the shielding transparent electrode between the liquid crystal panel 10 and the touch panel 20 causes transmissivity poor.
Moreover, as a variation of the touch panel attached type liquid crystal display device, first and second electrodes are formed on both sides of a touch panel glass substrate of the touch panel, and an additional insulating film is formed for protecting underlying electrodes and preventing noise from infiltrating. In this case, patterning of the insulating film on a backside of the touch panel glass substrate is also required for application of a signal, to cause problems in that additional steps, and material are required, and transmissivity becomes poor.
And, in a case the electrodes are formed on both sides of the touch panel glass substrate, the touch panel glass substrate is required to turn over for performing required steps, causing problems in that a process time period is increased, and defects, such as scratch or formation of foreign matter, increases.